Transmission issues

[Mooseman]

Just before I put it in storage, my tranny was giving me some issues. First, the backstory.

It now has 114k KM. I had it tuned in May 2020 and the tuner put the shifts really hard. I mean like chirp the tires at every shift part throttle hard. Drove it like that all that summer. Then last summer, it started flaring some shifts and noticed the TCC not holding steady, RPM varying 200-300 while cruising. Took it back to the tuner and he softened the shifts and ran the trans adapts. Seemed to have helped then but shifts still felt off. Also got the tuner to give me a copy of my OEM tune since I now have HPTuners. Also dropped the pan and replaced the filter and fluid. It was perfectly clean. When I replaced the fluid and filter when I first got it, it was normal.

Fast forward today, it's gotten worse after taking it out of winter storage with the battery disconnected. It flares on some shifts especially cold, TCC still fluctuates RPM and now it does a really weird thing occasionally where coming to a stop, it will either shift down when stopped, giving the impression I'm getting rear ended, sometimes twice, or it will be like in neutral when I try to take off again. Putting in N and then D does solves that. Seems to happen more coming from a highway drive.

Compared the current tranny tune to the OEM and it was basically stock except for a couple of shift parameters (3-4 I think). Changed those to OEM and it seemed to help a bit but still does the same. Next I'll try putting the whole tune back to stock, except DOD, in case it's a torque management thing.

Maybe when the tuner upped the pressures all over the place it damaged the sensors or solenoids in the TEHCM. I'm sure hoping it's not a mechanical failure.

I've watched a ton of 6L80E teardown videos and know that the torque converter can self destruct and send shrapnel through the pump and the whole tranny. Also know about the 3-5R drum that can crack the weld and leak. Never any of them talk about my specific problem though.

Just doing a search and I did find this that may point to a bad TEHCM:
https://forum.hptuners.com/showthread.p ... post561233

Sounds like you're moving in the correct direction. I'm quite happy with mine now, when it was acting up it was a major PITA. I had to replace the TEHCM in mine. It decided it didn't want to be part of the shifting program. Hard shifts, sliding shifts, go into neutral at a stop and then slam into gear.... you get the picture. Replaced with a Dorman reman be fine now.

Anybody have any ideas? I'm thinking of getting a TEHCM from a junker at the PnP yard and just swap it in to see if it changes anything before I dole out a ton of cash for a rebuilt. I do have the ability to program it.

[andrewquant]

I've rebuilt and tuned few 6L80s. First, since you have HPtuners, hook up via the cable (not bluetooth) and use the VCM scanner to command the TCC to lock while you are driving. It should show the PID for TCC pressure (normally 10-100 psi) to be over 500psi making for zero slip at all under any throttle position. If your PID for TCC slip shows more than 0 (+3/-3) rpm, then you have a TCC apply problem. Most likely the TCC frictions are worn out. If you suspect the TCC as the cuplrit, then set your TCC apply mph to 318 in all gears and write to the TCM (save the old config first to put back later). That will tell your TC never to lock. If the problem goes away, then you know. If it does not go away, then I would suggest you pull the pan again and this time also pull the valve body and do an air check. You need a special "torx plus" bit (size 10 I recall) to pull the valve body to access the air check holes.

The extra shift pressure wont hurt the solenoids or the sensors, but it can blow out a seal in the pistons for each clutch. Air check will help you find that. While you have the valve body out, check the pressure discs on the TECHM for cracks or tears. Also check the screen for debris. There is also zero reason for it to be shifting hard at part throttle. Thats tuner incompetency. You can set shift pressure based on torque, and you only ever add pressure at high torque levels. Also, stock shoft pressure it plenty. I'm running stock pressure on a car with 2x the stock power.

Thats about all you can do without removing the trans or opening up the valve body.

Here is a link to the ATSG manual PDF I used to help me learn the 6L80. It will have everything you need to check the mechanical part of it. https://shop.ukrtrans.biz/wp-content/up ... s/6L80.pdf

Good luck.

[Mooseman]

Hey @andrewquant, thanks for the tips. I just saw your post now, missed it somehow.

Today,as a test, I retuned the tranny so that the TCC never comes on. That seems to have calmed down the cruising RPM fluctuations. While it was relearning, I was getting a 3-4 shift flare and over time, it seems to have resolved itself.

Comparing the OEM and the performance tune, the tuner had maxed out all the pressures and turned off all torque management so the tranny may have been hurt. I am still suspecting that the TEHCM also got damaged, especially for the TCC. Still planning to get a TEHCM and swapping it in after inspecting the switch films and programming it to my VIN.

[andrewquant]

Cool. For the 3-4 shift flare that is slowly resolving itself via adaptives, thats good, but it means there may be a possibility that your 4-5-6 clutch pack is well worn. Its the smallest clutch in the trans so it has the least surface area to hold with and usually fails first. The adaptives are making up for the extra clearance in the pack, but they can only go so far. If it comes back (without doing a relearn) then get in right away to have that clutch rebuilt.

As far as the TCC testing results, it sounds like its working, but maybe your apply ramp table or desired slip table is wonky. Some tuners mess with that and some dont. Compare to stock and tell me what you see. Need to know what TC you have in there though to know if the settings jive. OEM or aftermarket. The TCCs are very different. I'd also go do a datalog. Set a PID for TCC desired slip, TCC slip, and TCC pressure and go for a drive. Post the datalog and I will tell you what I think about it.

[Mooseman]

I'm still in the learning stage and setting up the scanner is still a big mystery to me. I tried to set up some PIDs and got nothing. I'll have to read up and watch some YT videos.

BTW, I ordered switch films with the tool as well as new valve body seals. I think those are my problem. With the pressures as high as they were, they probably got blown out. Might not be till next week or so before I can tear into it.

In the meanwhile, I'm still gonna tinker with the tune. Seems to be behaving normally now with the stock tune. Now I want my engine power back so I have to keep the stock tranny tune while putting back the engine tune but with the torque management back on. Have to compare between the stock and performance tune.

[Mooseman]

So today I pulled the valve body and replaced the switch films along with new gaskets/seals. Turned TCC back on in the tune (used the stock tranny tune) and, nada. Still getting the 100-200 RPM fluctuation while in 6th between 60 and 80 KM/h. Above that speed, it either disappears or is undetectable.

Still haven't figured out how to set up scanners in HPT so I'll use my Tech 2 and have someone drive while I monitor pressures and slip and play with TCC engagement pressures and speeds. I'll see what happens when I program it to engage higher than 90 KM/h.

I have a feeling that the torque converter clutch is pooched and I'll have to drop the tranny to replace it. This won't happen this year with finances as they are. At worse I'll just leave it disabled.

[JoeR]

Like Andre says, you should see what the slip is when you command it on with the scanner. It should be very low, like less than 10 RPMs. If it's not, your converter clutch is very likely smoked. It's not very advisable to drive it forever in overdrive with the TCC turned off. It makes the trans run hot.
Joe

[elc32955]

Have you thought about tossing a tube or 2 of Lubegard in it to see what happens? Sounds like at this point you don't have much to lose.

Personally before I had the issues with the Tortoise tranny I had not heard of it, but two tubes later... problems cured! I did some research on it as a result and while not the proverbial silver bullet it's pretty darned close - unless you have physical mechanical damage with parts tinkling out of the case.

Food for thought....
Eric

[Fudgehog]

Moose, maybe you can try a bottle of Lucas stop slip too, I always had decent results with it.

Have you overfilled the transmission, as some members have had good results with as much as half a quart /liter over?

Did you do the Camaro pan/filter upgrade?

I also agree with the above post that VCM scanner by HPtuners should help command those solenoids/pressures.

For a relatively low mileage, I hope the previous tune did not damage your transmission admittedly I'm not a transmission wizard but just trying to think of possibilities.

[GammaFlat]

I am not a big fan of the fill procedure. I bought (but haven't yet installed) a trans dip stick for this reason. I have gotten flairs on 1-2. Is it correct to assume that could be low fluid? I do have the deep pan. I was not pleased with the color of the fluid when I installed the pan (with less than 60K miles), so I'll be doing a fluid change again soon.